i am making the methanolic extract of withania somnifera leaves but what i am getting in the end is the paste.i want to know how to bring the paste into powder form???

-ujla80-

you can dry the paste under vacuum or lyophilize.

or, if what you're looking for isn't labile, just let it dry on the bench. residual methanol should evaporate quickly (unless there are a lot of lipids in the extract in which case you may have to delipidate the paste before drying).

-mdfenko-

dear mdfenko

we can't lyophilize methanolic extract because only aquous extracts can be lyophilized because lyophilization is the dehydration by deep freezing (-80) under vaccume.

-ujla80-

methanolic extract of withania somnifera (ashwagandha)

- try saying that after a couple of pints

-Dominic-

ujla80 on Jun 26 2009, 11:46 PM said:

dear mdfenko

we can't lyophilize methanolic extract because only aquous extracts can be lyophilized because lyophilization is the dehydration by deep freezing (-80) under vaccume.

okay, then you can speedvac the paste to dryness.

-mdfenko-

I assume you have done eveporation of MeOH using rotovap? The reminder is mostly solid/oil substances that you are interested plus some water if it is orginated from fresh plant material, so lyophilization should be OK.

-genehunter-

I agree with genehunter, most of the methanol should already be gone, what is left will not affect the lyophilization. I was always warned about not putting solvents through the freeze drying pumps but when I arrived at my current lab (dominated by chemists) I found everyone quite happy to load solvent filled HPLC fractions straight on with no major dramas.
Getting back to your original post; with some methanolic plant extracts the only way I’ve found to get rid of the ‘paste’ is to do a solvent partition with something like hexane.
The other tip I can offer would be to keep the methanol cold while performing the extraction.

-DRT-

thank you all

it never occured to me that i can lyophilize the paste...now i'll try it.